The aerosol consumer package goods market has enjoyed excellent growth and profits since the early 1950's. However, recent consumer research has indicated a growing ground swell of negative attitudes towards aerosols in general. Specifically, the consumer is most concerned about:
A. the rising costs of aerosols with diminishing "apparent value", PA1 B. product malfunctioning including valve clogging and/or failure to dispense all of the contents, and PA1 C. overpackaging, i.e. the aerosol form does not contribute to product performance, rather it is viewed as an expensive "convenience".
Therefore, it is not surprising that the growth in certain aerosol categories such as air fresheners and pesticides has started to soften. Particularly noteworthy has been the vulnerability of these categories to non-aerosol new product introductions. Examples include, pesticide strips and solid air fresheners. Consumer research has shown that the success of both of these non-aerosol products was due primarily to the consumer need for a "continuing" or ongoing type of performance as opposed to the fleeting performance of aerosol sprays. This is understandable since many pesticide and odor problems are lingering in nature and require continuous treatment. Such treatment can be annoying and time consuming. The various solid products were designed to respond to the consumer need for continuous long term treatment. These solid products have performance limitations and generally are a compromise in performance in that they are limited to the volitalizing properties of the carrier and the active materials dispensed.
While a large number of intermittent unattended or automatic aerosol dispensers have been the subject of patents; applicant is unaware of a single such device other than those utilizing expensive electrical timers, which has had commercial success. Cost has been a major problem; however, there are multiple problems inherent in the discharging minute quantities of an aerosol borne product. For one thing it is difficult with conventional flow control means, such as needle valves, to attain the sensitivity of adjustment required to deliver extremely small quantities of product. Also it is difficult to reproduce prior adjustment if the stem of the needle valve is moved. Another problem is to discharge at reasonably constant spacing between discharge, particularly if the spacing is measured in hours or days and the total period of operation may be several weeks or months. Another problem is to produce a crisp discharge free of initial or residual low pressure dribble or trickle of the liquid product which would produce spots adjacent the dispenser, or dry in the minute discharge passage and clog further operation.
Also, because of the wide range of products and propellents, and their physical properties, the problem of producing an unattended aerosol dispenser which will meet the requirement of a variety of products and propellent has heretofore not been accomplished; for example, the components of some aerosols are in a single liquid phase in the container; that is, an essentially homogeneous mixture. The components in other types of aerosol products are present in dual fluid phase; that is, the propellent is separated from the product and collects at the top of the container in a gaseous phase, and the product collects at the bottom of the container in a liquid phase for discharge through a dip tube. In the case of single phase aerosols at some stage of discharge a gaseous phase may collect at the top of the container due to pressure drop.